The present invention relates to a new and improved construction of controllable phase shifter. More specifically, the controllable phase shifter of the present development is used for an alternating current-transmission system, especially for a line or power network, wherein there is provided a number of reactive impedances connected with the lines of the transmission system and a valve switching device which can be controlled with respect to the phase shift angle which is to be set.
The hereinafter premised features will be found, for instance, in the generally known chokes which can be switched between taps or can be periodically turned-on for controllable intervals by means of semiconductor-switching valves, especially thyristor or triac switching valves, in order to thereby control the effective inductance of such chokes. Such type reactance elements are employed, for instance, in energy transmission lines in order to improve the transmission characteristics. Further, appropriately constructed reactance transformers are used, for instance, for the transient increase of the torque at synchronous generators and for the purpose of improving the stability of compound operation.
The mentioned equipment is associated with the drawback that there is required a comparatively high expenditure in equipment components, especially when using chokes or transformers with taps. This is directly opposed to the desired wide field of application for power line networks and for other fields of use.